fix: more unique temp_file

src/exercise.rs

@@ -11,10 +11,15 @@ const I_AM_DONE_REGEX: &str = r"(?m)^\s*///?\s*I\s+AM\s+NOT\s+DONE";
 const CONTEXT: usize = 2;
 const CLIPPY_CARGO_TOML_PATH: &str = "./exercises/clippy/Cargo.toml";
 
-// Get a temporary file name that is hopefully unique to this process
+// Get a temporary file name that is hopefully unique
 #[inline]
 fn temp_file() -> String {
-    format!("./temp_{}", process::id())
+    let thread_id: String = format!("{:?}", std::thread::current().id())
+        .chars()
+        .filter(|c| c.is_alphanumeric())
+        .collect();
+
+    format!("./temp_{}_{}", process::id(), thread_id)
 }
 
 // The mode of the exercise.